1. Field of the Invention
The present invention relates to a data communication unit using a light-emitting diode for data communication, and an electronic device.
2. Description of the Related Art
Conventional communication systems of data communication units using a light-emitting diode include an infrared communication system and the like standardized by IrDa (Infrared Data Association). This infrared communication system by IrDa uses a light-emitting diode that emits light for data transmission and a photosensor that receives light from a light-emitting diode of another electronic device, and is adopted in electronic devices such as personal computers and mobile phones.
A photosensor and a light-emitting diode are basically semiconductor devices having a PN junction. Therefore, by using a light-emitting diode, it is also possible to receive light, as disclosed in a Japanese Patent Application Laid-open No. 2001-119063 (Abstract, Claims, Detailed Description of the Invention, Drawings, and so on hereinafter referred to as “patent document 1”)
The light-emitting diode and the photosensor used in the aforesaid infrared communication unit are disposed on a surface of the electronic device for communication with another electronic device having a communication function. Therefore, providing an electronic device with the infrared communication function standardized by IrDa will be a cause of hindering downsizing of the electronic device and restricting space use efficiency. It will also be a cause of cost increase.
An electronic device generally has a light-emitting part such as a power indication lamp. As this light-emitting part, a light-emitting diode outputting visible light is generally used. Therefore, in order for an electronic device not having a data transmission function to have a data reception function, the electronic device needs to have, on its surface, the light-emitting diode emitting visible light and a photosensor for data reception. The same problem as the aforesaid problem also occurs in this case.
The art disclosed in the patent document 1 is simply to utilize one LED both as a light-emitting element and as a light-receiving sensor. The patent document 1 has no description regarding communication. The patent document 1 does not solve various problems involved in providing the aforesaid communication function.